Exploring the use of adjusted body mass index thresholds based on equivalent insulin resistance for defining overweight and obesity in UK South Asian children

BACKGROUND: Body mass index (BMI) overweight/obesity thresholds in South Asian (SA) adults, at equivalent type-2 diabetes risk are lower than for white Europeans (WE). We aimed to define adjusted overweight/obesity thresholds for UK–SA children based on equivalent insulin resistance (HOMA-IR) to WE children. METHODS: In 1138 WE and 1292 SA children aged 9.0–10.9 years, multi-level regression models quantified associations between BMI and HOMA-IR by ethnic group. HOMA-IR levels for WE children were calculated at established overweight/obesity thresholds (at 9.5 years and 10.5 years), based on UK90 BMI cut-offs. Quantified associations in SA children were then used to estimate adjusted SA weight-status thresholds at the calculated HOMA-IR levels. RESULTS: At 9.5 years, current WE BMI overweight and obesity thresholds were 19.2 kg/m(2), 21.3 kg/m(2) (boys) and 20.0 kg/m(2), 22.5 kg/m(2) (girls). At equivalent HOMA-IR, SA overweight and obesity thresholds were lower by 2.9 kg/m(2) (95% CI: 2.5–3.3 kg/m(2)) and 3.2 kg/m(2) (95% CI: 2.7–3.6 kg/m(2)) in boys and 3.0 kg/m(2) (95% CI: 2.6–3.4 kg/m(2)) and 3.3 kg/m(2) (95% CI: 2.8–3.8 kg/m(2)) in girls, respectively. At these lower thresholds, overweight/obesity prevalences in SA children were approximately doubled (boys: 61%, girls: 56%). Patterns at 10.5 years were similar. CONCLUSIONS: SA adjusted overweight/obesity thresholds based on equivalent IR were markedly lower than BMI thresholds for WE children, and defined more than half of SA children as overweight/obese.